Author Topic: Would it have been a good idea for FH to be like Angara (i.e. 5-core)?  (Read 23840 times)

Offline spacenut

  • Senior Member
  • *****
  • Posts: 2350
  • East Alabama
  • Liked: 388
  • Likes Given: 228
I would think that Russia has limited resources to build bigger rockets.  They also try to use existing manufacturing capabilities.  Therefore due to manufacturing capabilities, they have limited size rockets, cores, and they transport most everything via rail for lower costs.  They have their problems.  SpaceX doesn't need a 5 core vehicle.  If they want to achieve SLS or Saturn V results, they can simply build a bigger rocket, thus BFR. 

Another thing.  It is hard enough to get the first stage to land and be reusable.  With a five core vehicle it would be even more of a headache for SpaceX.  Falcon Heavy is to land the outer stages back on land, and the core on the drone ship.

If they want more throw weight for F9 or FH, they can develop a metholox second stage.  No need for more cores. 

Offline Pipcard

  • Full Member
  • ****
  • Posts: 474
  • Liked: 119
  • Likes Given: 98
If SX's BFR comes off as they say, its likely that its excess capacity would address the next hundred years of launch capacity! It will be damn hard for any other LV to exist in its shadow.
I brought up to fredinno the idea of a fully reusable BFR being a "one-size fits all" rocket (once reusability ops have matured enough), able to supplant any multi-core/dial-a-rocket system and launch any payload (which would also help with flight rate). He told me that (bolded for emphasis)

Quote
Just because you can launch everything on one rocket, doesn't mean you should. Even for a fully reusable rocket, a single 29T rocket (if the rocket is full CH4 or RP-1, a rocket with a H2 2nd stage can settle for a lower LEO payload capacity, like 25T to LEO, due to superior GTO capacity)

Let's use the IXV example again. How in the WORLD would you give it secondary payloads? It would be a 1-2T payload on a rocket designed for 29x its payload capacity. Assuming full reuse, you still have to build a rocket every ~10 flights, and the massive rockets are harder to maintain (w/ F-1 sized engines).

Reuse doesn't remove costs. It only saves optimistically 40% in cost (both stages). The rest of the cost structure, like testing and inspection, get larger- testing a larger engine of a TSTO RLV is more expensive. It also increases the complexity and integration costs you seem to be so worried about, since deploying 10 satellites is more complex than orbiting one, and larger rockets are more complex and difficult to develop.

Because launching multiple payloads on one mega-rocket would be "more complex," he also considered how ridiculous it would be to launch a single 2-tonne payload on a >100-tonne capacity rocket.

Quote
Imagine launching an SLS to launch IXV :D

You make me chuckle. You probably could use the SLS core as a reusable SSTO and launch IXV!

On a serious note, who would do that? I can't see SpaceX spending 500 Million dollars making a rocket, only to then launch 5T satellites. That would cost mare than any F9.

It seems similar to the attitude that the Shuttle would reduce costs to launch, and everything should launch on it, because it was 50% reusable (including the "reusable" SRBs), even though it needed every single launch it could possibly get to break even with commercial launchers.

I don't know how he managed to come to this conclusion that full reuse only saves 40% over expendability.

Nor do I know how people on this forum determine that a reusable BFR will be as cheap or cheaper than a Falcon 9 launch.

It all depends on how affordable it turns out to be for turnaround of monstrous 10-15m (IIRC) rocket stages, which is a huge leap from the 3.66-m cores SpaceX is using now.

Right now, SpaceX "hopes to" save about 30% for reusable Falcon 9. Is this the limit? With full reuse (along with higher flight rates), would they be able to achieve the kinds of costs that would enable a BFR to launch all sorts of payload masses without concerns of overcapacity?
« Last Edit: 07/19/2016 08:31 PM by Pipcard »

Offline envy887

  • Senior Member
  • *****
  • Posts: 4122
  • Liked: 2131
  • Likes Given: 1273
deploying 10 satellites is more complex than orbiting one[/quote]

Well, obviously. It's cheaper to launch 1 sat than 10 of them. But launching 10 sats on 10 launchers requires integrating, launching, and deploying 10 sats, just like launching 10 sats on one launcher.

Quote
It seems similar to the attitude that the Shuttle would reduce costs to launch, and everything should launch on it, because it was 50% reusable (including the "reusable" SRBs), even though it needed every single launch it could possibly get to break even with commercial launchers.

Comparisons to Shuttle should be thought through a lot more carefully. BFR won't be crippled by DOD and Congress requirements, won't be 50% expendable, won't have a $250 million drop tank, and won't have solids, and it will be able to launch directly to GTO and probably directly to GSO.

Quote
Right now, SpaceX hopes to save about 30% for reusable Falcon 9. Is this the limit?

Probably not, since the S1 is 75% of launch cost. But they are still throwing away everything above the interstage, which is some $15-$20 million in costs or every commsat mission. BFR won't.

Offline Space Ghost 1962

  • Senior Member
  • *****
  • Posts: 2783
  • Whatcha gonna do when the Ghost zaps you?
  • Liked: 2903
  • Likes Given: 2249
If SX's BFR comes off as they say, its likely that its excess capacity would address the next hundred years of launch capacity! It will be damn hard for any other LV to exist in its shadow.
I brought up to fredinno the idea of a fully reusable BFR being a "one-size fits all" rocket (once reusability ops have matured enough), able to supplant any multi-core/dial-a-rocket system and launch any payload (which would also help with flight rate). He told me that (bolded for emphasis)

Quote
Just because you can launch everything on one rocket, doesn't mean you should. Even for a fully reusable rocket, a single 29T rocket (if the rocket is full CH4 or RP-1, a rocket with a H2 2nd stage can settle for a lower LEO payload capacity, like 25T to LEO, due to superior GTO capacity)

Firstly, fredinno hasn't been effective in supporting his opinions, nor in coping with experts and references in this thread. He cannot even accept input from those closest to his position. It is hard to have a discussion with someone who appears as a troll often.

His disguised argument seems to be about efficiency to orbit, which you can only prove with the flight history of a deployed vehicle. This is primarily the basis for Atlas V and hoped to be carried forward into Vulcan. From actuals with Angara, it appears not to be the case in practice. Perhaps after a decade in service, in over a decade, they might have a hydrolox stage and reduce the mass fraction on the propulsion module such that it is more so.

He misses the point about SX's approach. They don't care to be efficient to orbit at no economic cost. They are attempting economic to orbit. There's a 1000:1 cost amplification for a simple LH fitting that won't be made up on volume, for example.

Quote
Quote
Let's use the IXV example again. How in the WORLD would you give it secondary payloads? It would be a 1-2T payload on a rocket designed for 29x its payload capacity.

The ultimate goal of "generic launch" is all payloads are secondary payloads. And that non traditional means are used to distribute them after unity launch. His ideology won't allow this, thus the "troll" reaction. I can't "understand it for him", and consider his perspective as quaint and "old fashioned". He's welcome to tilt at windmills while we see how things work out.

Quote
Assuming full reuse, you still have to build a rocket every ~10 flights, and the massive rockets are harder to maintain (w/ F-1 sized engines).

They don't have F-1 sized engines. And it may be the case that you can get to thousands of flights with a certain larger vehicle strategy, with a more lofted trajectory that will infuriate him even more by the non optimization it would reflect to him (slower vertical, then horizontal). I think when Musk reveals, he'll probably have a stroke.

Quote
Quote
Reuse doesn't remove costs. It only saves optimistically 40% in cost (both stages). The rest of the cost structure, like testing and inspection, get larger- testing a larger engine of a TSTO RLV is more expensive. It also increases the complexity and integration costs you seem to be so worried about, since deploying 10 satellites is more complex than orbiting one, and larger rockets are more complex and difficult to develop.

His idea of reuse is dated and colored by both Shuttle and F9 ELV/RLV operation. His idea of on orbit operations doesn't take into account the logistical changes in applying a Mars deep space vehicle for donkey work in deploying a few hundred to thousand secondary payloads over perhaps a week, with other missions concurrent. Very different operations for a logistical end gain. He'll waste delta-V like a drunken sailor - who cares, a Mars vehicle uses lots of consumables/props anyways, so slumming being wasteful around Earth/Moon is fine.

Its like someone with the concept of a pickup truck imagining a semi tractor trailer rig (or lorry) using it the same way, as in point to point deliveries through a single hub serving an entire continent. Very naive.

Reuse does not need to resemble even remotely ELV. BFR doesn't economically work like SLS/Saturn V/Energia. And that's the key to this all. He's just betting that the bigger you go, the costlier everything gets. Ed Kyle shares that view BTW, and so do others.

Use Falcon as a hint here. SX handles things as much as commodities as they can, where scale of vehicle limits. They have used it as a platform to prove BFR, such that even more commoditization can occur. This is unlike past approaches, where the scaling up of the "bigger hammer" was endured to briefly run a huge vehicle with an enormous cost. Govts can do that. Look at the NIF. If you want to do a narrow inertial confinement experiment, you can do it for a billionth of the cost.

Private industries don't work that way. They can't even think that way, or they don't survive.

Quote
So he's one who doubts reusability can offer much savings, even with reuse of both stages. I don't know how he managed to come to this conclusion. Nor do I know the methods by which people here come to the conclusion that a reusable BFR will be cheaper than a Falcon 9 launch.

Because he's stuck on a metaphor that isn't applicable. Many are. Possibly an article of faith. Fine to be a flat earther. Good luck with that. Not wise to conflate entirely different approaches, forcing them to work identically when they are not.

Keep in mind that Falcon is a stepping stone.

Kinda boring answering this guy/troll. Look, not even Musk knows if everything will pan out. Might not.

Where I would challenge Musk isn't in the efficiencies to orbit. Its in the effectiveness of growing the payloads to orbit that pay for BFR operations - we'll have to see a considerably more active aerospace industry that works at one hundredth of the cost profile than before. He might come close to killing it before the renaissance occurs. That's where you can be most skeptical.

But one must at least stretch to understand the "why". The root of the "why" Musk has always said - you can't get to Mars with the economics of a non-reusable system. So the first act of this passion play is to remake the launch provider as driven by reuse - full stop. Believe it or don't believe it.

fredinno doesn't. End of story. The rest are rationalizations. They are being erased. Nice to see.

edit: fix quotes, arrrgh!
« Last Edit: 07/19/2016 09:13 PM by Space Ghost 1962 »

Offline Kansan52

  • Full Member
  • ****
  • Posts: 1083
  • Hutchinson, KS
  • Liked: 328
  • Likes Given: 386
Thanks for a very thoughtful summation!

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32243
  • Cape Canaveral Spaceport
  • Liked: 10898
  • Likes Given: 325

Also, I'm going to go back and reply more later, I'm doing exams, and don't have time now TBH.

You need to do some more studying because you are failing here.

Offline envy887

  • Senior Member
  • *****
  • Posts: 4122
  • Liked: 2131
  • Likes Given: 1273
...
Nor do I know how people on this forum determine that a reusable BFR will be as cheap or cheaper than a Falcon 9 launch.
...
Because F9 will always throw away the upper stage, and BFR will not.

The goal for Falcon 9 is 10 flights without refurbishment, and 100 flights on the airframe with some part replacements. That only applies to the booster, which costs somewhere between 30 and $45 million. That implies 1% of parts have to be replaced each flight, on average, and assumes the entire cost of the booster is parts (which is very conservative). With that, we can swag some rough expended costs for a Falcon 9 RTLS reusable flight:

Fairing: about $5m (might be lower with reuse)
Fuel: about $0.2m (per Musk)
Upper stage inc. payload adapter: about $10m
Refurb parts: about $0.4m (1% of booster cost)
Refurb labor: about $0.2m (40 techs working for 2 weeks)
Launch operations: about $2m (includes test fire, range, S2/payload integration, LZ to LC transport, etc)

Total: $17.8m

If BFR is an order of magnitude bigger, and BFS 5x bigger than F9 S1, and cost scales with size, we can estimate some similar prices:
Fairing: $0 (probably won't have a fairing as recloseable doors are likely... cost goes to S2 refurb below)
Fuel: $2m (10x Falcon 9)
Upper stage refurb parts: $4m (2% of cost, inc. reuseable payload adapter/dispenser)
Upper stage refurb labor: $2m (400 techs working for 2 weeks)
Booster refurb parts: $4m (1% of cost)
Booster refurb parts: $2m (400 techs working for 2 weeks)
Launch ops: $15m (NO test fire, includes range, payload integration, LZ to LC transport, etc)

Total: $34.0m, so for 2x the F9 RTLS cost they get 10x the performance to LEO or GTO.

These numbers don't have a lot of solid basis (any help firming them up would be greatly appreciated), but an order of magnitude cheaper than STS for similar IMLEO seems reasonable considering SpaceX is close to that ratio with expendable Falcon 9. No LH2, no humans flight, and vertically integrated manufacturing all help a lot.

Tags: